[lld] [lld][ELF] Merge equivalent symbols found during ICF (PR #139493)

[Fangrui Song via llvm-commits]

MaskRay wrote:

I typically prioritize correctness too, but exposing OffsetGetter and needsGot from Relocations.cpp is completely unacceptable.
The distinction between local and non-local symbols is also troubling.

I generally prioritize correctness as well, but exposing `OffsetGetter` and `needsGot`/etc from Relocations.cpp, along with the concept of "trivial relocation", is entirely unacceptable.
The local versus non-local symbol distinction is also problematic, as it keeps potential correctness pitfalls.
I believe the added complexity isn't justified. Has the MachineOutliner issue been resolved? Fixing it would also address COFF and Mach-O.
Obtaining ABI approval would be ideal, but on the compiler side, we could treat separate R_AARCH64_ADR_GOT_PAGE and the paired relocation as incorrect and avoid generating such code sequences.


https://github.com/llvm/llvm-project/pull/139493